US2656650A - Sealing apparatus - Google Patents

Description

Oct. 27, 1953 J. F. DE ANo 2,656,650

SEALING APPARATUS W M? HIS ATT NEY OC- 27 1953 J. F. DE ANo 2,656,650

4 :sxezALING APPARATUS Filed NOV. 20, 1951 2 Sheets-Sheet 2 INVENTOR: JOHN F. DE ANO hwg? HIS ATT RNEY.

Patented Oct. 27, 1953 4.mlm ne Ano, Melrose. :Para nl., assignor to The :Bauland "Corporation, 'a corporation of Illinois animation November zo, 1951, se'riai 257,354 ,is claims. (c1. .t9-2) 4','lfhis"invention relates toisealinea'pparats 'lisefulfin lthe manufacture df electr disliargede- :vices Vandgrnore particularlyfto appafiatn's forfseal; ing electrodes'ystems intovthewenvelopes of belee- 4tr'pn-discharge devices. The"invent-if` l 'A c abl'e to thedlinanufajctre of wide variety :di *electron-discharge devices, Stich as conventional transmittingand receiving-type tnbe's, brit` is particularly useful in the fabrication o'fcathode-ray tubes and will therefore be described in that connection. f n y.

A cathode-ray tube 4comprisestwo maior 'snub'- assemblies which lare i.isally, `fabricated separately and j'oil'ied 4toethei' 'only in a la-terstag vvof the 'manufacturing process. Cnfe ofthfse sub'- assemblies is the outer ""ishell, or envelope, 'ofthe tiibe; the other isth' 'electrodejsystenn or elec'- `tron The envelopevcomprisesa cone por; tion carrying aYiioriescentscreen-bearing face plate and a cylindricalglajss neck portion {adapt} fed to receive the lcton :gun- `The electron gun is composed ofsvrai parts, constituting die various electrodes ,of the systern, which are usd- 'ally assembled and "fiX'd to v a ydise-like jgiasfs "mount designed ftdbe sealed into/,the neel;l of the envelope. When 'the electron 'gnnasseinbly and tube envelope are both ,cornpvleted` thereare fused Voi' sealed together, fusally through the iiseoi semi-automatic vrriaohinery. .After peeling, the tube envelopes .aifeusoaiiy sutj'eted .to runner heattreatment toann'ealth' :glassandfstrengtlien the sealing bond, following .which th y are .evacuatefd, gettered,4 and based in aceord'a'l'ewtli welll'- dustry.

l may' te, annif ted byimmdiate damage t@ te? a'sse d ofthe @litterature at each p ing station 'inthe saiiiigandanneal- 4Diioess essential to. prevent `los"sesww "ch rnient onirwise fesuit frein news diie htok pioper namteriafititne 1ii;itt-tiesnogL cypra vinile cntoiorsiieh news is an important een. sidratinn in the manufaetur of an types of eicetoii-dis "ree devises, it is ef sementi import in este of animos-inf tutes` ind the ententes-fof these-totes fesait spessi @sin treatment prior 'to-final ssinti; nannies: a cathode-'ravine at th final assemny stage risnts notiiely the loss ofA a glass envelope btt the iets of a attenant ratejr in- 've'stiht due to the appeciatin in 'value ocr'clafsion'ed by application `'of .fa riiuorescent yscreen and fan linternal 'conductive coating.

4De'terr'r'i'ination of these :highly critical `processlirligi temperatures is l'not practical through maintenanc'e :o'f `peri-nanern-,ly installed individual `tempaturemeasurin'g devices "at ieach 4of the operating stations, 'since the work-holders utilized Vin transferring 'the vtubes .from 'station to station are required to rotate to provide for even :heatingu/of thegl'a'ss This rotation would `create mechanical interierence between 'any stationary device andthe Work-holders. Consequently, it has been the `fiisi'ial `practice inthe fart to utilize Ta contact pyronieter inserted inturn Vat teach operating vstation vto ldetermine the `temperature Apitoduced by :theheat source atthat station. This niethod is inherently awkward in that it Te- 'quire's the'operator properly to position the py- 'rnieter and simultaneously to `note andrecord the temperature. The method 'has afiurther -disladvantage in that insertion of the :pyrom'eter curate temperature determinationfhas required tf1? inbriymnt o'ftwo persons, one to position the pyrorne'tr and the othe'rtoi take readings,

`since a single operator would iind it `virtually 'nipos'sibleto "note the position 'of `tlie vpyrometer iandrsirnultaneously to take the necessary ,reading- It Aisa primary object of 'the `present invention to provide a new and improved apoaratixs` for sealing'electrode `systems into electron-"discharge device envelopes.

It is a `more specific object 'of the invention to provide anew and improved device for the aen'rate determination of heat-treating temperatures `at thevarious `operating 'stations in apparatjds for sealing electrode systems :in `electron-discharge device envelopes.

It is 'a farther vobject of the invention to provide apparatus capable of achieving `this accuracy ofl temperature determination withiit the necessity 'of incorporating elaborate and` expensiveidevices or a multiplicity of devices andrwhich will require a minimum of time and skill on the part of the process operator.

-Tlie invention accordingly provides vapparatus for sealing electrode systems in electron-.discharge device envelopes', which apparatus .in-

cludes a. plurality of operating stations, each having at least one` localized heat source, `arranged in predetermined sequence for subjecting the envelopes to a predetermined heat-treatin'geycle.

3 The apparatus also includes a plurality of spaced rotatable work-holders, relatively movable with respect to the operating stations, for transferring the envelopes and electrode systems to each of the operating stations in sequence. A driving apparatus is provided to effect rotation of the workholders. A support member, generally simulating one of the envelopes in physical configuration, is removably installed in one of the work-holders, and a temperature-indicating device is mounted on this supp-ort member. A thermally sensitive device is operatively connected to the temperature-indicating device and fixed to the support mem-ber in such a position that it registers the heat treating temperature at the particular operating station momentarily occupied by the work-holder in which the support member .is currently installed. Friction coupling means is provided between the driving apparatus and the support member to permit arrestment of the rotation of the support member independently of rotation vof the remainder of the work-holders.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims but its organization and manner of operati-on, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawlings, in the several figures of which like elements are indicated by likereference numerals, and in which:

Figure 1 is a view, partly schematic, of a portion of a sealing machine constructed in accord- Iance with the invention, showing two operating .stations at one of which a cathode-ray tube is Ibeing processed and at the other of which a teinlperature determination is being made, and

Figure 2 is a sectional View oi the temperaturemeasuring portion of the apparatus of Figure The sealing machinery of the present invention may consist of a number of operating stations each comprising a localized heat source. The

Aheat sources are preadjusted to suitable operating vtemperatures in accordance with a predetermined heat-treating cycle. AV plurality of work-holders .are used to support a tube envelope and an electron gun mount assembly in suitable juxtaposi- -tion at each of the operating stations and are the work-holders on a rotatable circular turn-A table within the circle formed by the operating v stations..

In Figure 1, only two operating stations lil and II of such an apparatus are shown, it being understood that a sufficient number of additional similar operating stations, not shown, are also provided to perform the several steps of the sealing and annealing process. Two work-holders I2 and I3 are shown at operating stations lil and i l, respectively, and are mounted on a turntable I4 which is arranged to transfer work-holders I2 and I3 from operating station to operating station as by means of a motor drive system (not shown) or in any other suitable manner. Workholders I2 and I3 are arranged for continuous rotation, as indicated by arrows I5 and I6, by means of a linkage Il', such as a chain drive, a belt drive, or other similar power transfer means, actuated by a power source I8, which may be an electrical .motor or any other suitable source of mechanical power. Power source I8 and linkage Il constitute the driving apparatus for rotating work-holders I2 and I3 and the remainder of the work-holders (not shown). A pair of gas jets I9, or other localized heat source, are provided at operating station I0 and are connected to a source (not shown) of suitable gaseous combustible material in any known fashion. Similar heat sources are provided at each of the operating stations.

Work-holder I2, in position at operating station I0, comprises a base 22 which is rotatably mounted on turntable I4. Rotatable base 22 is provided with suitable connection means such as a sprocket 28 to complete a mechanical coupling to linkage I'I and thus effect transmission of the `power necessary for rotation. An intermediate ring 23 is supported by a pair oi rods 24 mounted on base 22, anda clamp base 25 is adjustably suspended from ring 23 in a position somewhat above localized heat source I9. A clamp 26 is mounted in the center of clamp base 25, the central opening formed by the two sides of clamp 26 being generally circular in shape. An envelope support ring 27 is adjustably mounted on intermediate ring 23.

A cathode-ray tube envelope 28 is inserted in work-holder I2, the upper or cone portion 29 of the tube envelope resting on envelope support ring 21 and the lower or neck portion 32 of the cathode-ray tube 28 being engaged by clamp 26. Since the dimensions of cone portion 29 and neck portion 32 of cathode-ray tube 28 may vary with the particular size of the tube being processed, the exact positioning of envelope support ring 2 and clamp base 25 with respect to intermediate ring 23 may require adjustment in order to bring neck portion 32 into proper juxtaposition with localized heat source I9. This adjustment has been provided for by the adjustable mounting of these members with respect to intermediate ring 23 through the medium of several threaded adjustment rods 33.

A vertically movable plunger 34 is mounted on base 22 and is rotatable therewith. Plunger 34 serves as a support for an electron gun mount assembly comprising an electrode system'36 shown schematically in the drawing, and a glass mount 31. The vertical position of plunger 34 is regulated to locate glass mount 31 in suitable juxtaposition with localized heat source I9.

Work-holder I3 at operating station II is constructed in the same manner as work-holder I2 at operating station I0. However, work-holder I3 supports a temperature-determining device 38 instead of the cathode-ray tube envelope supported in work-holder I2. Temperature-determining device 38 comprises a support member generally simulating a cathode-ray tube envelope in physical configuration. A cone portion 4I 'of temperature-determining device 38 is retained by the work-holder I3 in a manner similar to that in which cone portion 29 of cathode-ray tube 28 is held in work-holder I2, and a neck portion 42 of temperature-determining device 38 is clamped in work-holder I3 in precisely the same manner as that employed in clamping neck portion 32 of cathode-ray tube 28 in work-holder I2. A thermocouple 43 or other thermally sensitive device is fixed to neck portion 42 in a suitable position to register the heat-treating temperature at each operating station in sequence .as turntable I4 is rotated to transport workliolder I3 from station to station. A temperature-indicating device 44, operatively connected to thermocouple 43, isl mounted on the periphery of cone Pportion 4I in afmanner tofbe lmore fully described in connection with Figure -2.

Hfn `carr'y'nig out the sealing process, -cathoderay A'tube envelope 2;8 is mounted'in the workholder as indicated, vthe position of envelope supportring 21 and clamp base 25 being so adjusted as 4to place Yneck portion 32 of envelope 28-in -position -to fbe heated Aby the flames from gas jets I8. Electron gun mountassembly 38,31 isplaced Aon vertically adjustable Aplunger 34 and plunger `v34 `is adjusted -to-place glass Vmount 31 rin such position thatit is also heated `by the flames from ==hea-t source I8. If it is assumed that operating station I0 -is the initial :stage of the process, the temperature of neck portion 32 andfglass mount 31 is--increased over room temperature by a pre- `-cietermined amount while the work-holder occupies this particular operation station. After `apredeterrnined time during Awhich the tem-pera-tureof these parts is increased to the maximum i and glass-mount 311 -is increased until work-holder Il.,

`I2 Vreaches an operating station `which main-- `tains a temperature suiiciently high to permit fusion of glass neck portion 3'2 and glass mount 31. At this opera-ting station, a further short movement of plunger 34 raises glass mount 31 -until its periphery :is in contact with the inner vsur-face of neck 32. At this operating station, therefore, mount 31 and neck 32 are fused together-and the electron gun mount assembly is etectively sealed into the envelope. Further operating stations in the complete process provide a graduated lowering Yoi" the temperature of thenow-fused mount 31 and neck portion 32 and fi'urther serve to anneal and, strengthen the newly -formed bond `between these two members.

-The progress of work-holder I3 through the `sealing and annealing stages is performed in exactly `the same manner and sequence as that Iol- 'lowed by work-holder I2. When the work-.holder occupies operating station II, the position or" -thermooouple 43 makes it possible to determine the exacttemperature to which next portion 32 `and glassmount 31 `willbe subjected when they reach operating station II. This determination `of the heat treating temperature at operating station `II is effected by noting and reading temperature-indicating device 44, since this device `is`-operatively connected with thermocouple 43.

.As work-holder I3, and therefore temperature- 4determining device 38, proceeds in sequence 'through the operating stations of the sealing and `annealing apparatus, a series of Vtemperature readings are made Yand gas jets I8 are adjusted until the temperature readings conform with the ndesired temperatures of the heat-treating cycle, Thus, an exact record of the temperature at each of the operating stations in their proper sequence is obtained and precise adjustment of `each heat source is effected.

Figure 2 is a sectional detail view of temperature-determining device 38. As previously indicated, a temperature-indicating device 44 is vmounted on the periphery of coneportion4l and -thermocouple 43 is `ilxed to neck portion 42 of device 38. A pair of flexible connector leads 45 provide fanioperattve wconnection between :thenmocouple 43 .and temperature-indicating 44 so that device 44 `registers the operating mmperature at the position `occupied :by thermo,- couple 43. `Neck portion '42 `is slidahly supported within an vextension 18 of xcone aportionM, :and a thumb :screw 4I6 L-is provided extension 4.8 for vfixing neck portion '42 to cone portion r4I While permitting Avertical adjustment o! thermol couple 43. A plurality of outwardly extending flanges .41, or alternatively a single peripheral loutwardly extending ange, :are axed `to .cone portion 4.1, and a frame ,member 48 4is retained A-in peripherally encompassing :relation `:with portion l41| by flanges 41. A 'plurality of `:rotary bearings .49 are mounted on framexmember v48,-t0 .engage cone portion A4I ,and provide coupling between cone portion 4I and trame member ,48 .whendevice 38 is installed inane of the work-holders. Frame member 48 -Js so formed as to fit on envelope support ring :21 and supports cone portion 4I through the frictional `couplingcf bearing 4.9. Another .rotary bearing 52 is mounted with an inner race 53 in engagement with neck portion 42 and provides means for frictional coupling between neck pont-ion 42 and .the work-holder through `an outer race 54 of` bearing 52 which is engaged by clamp 28 (Figure '1) AS previously mentioned, the physical confgration of the tube envelopes .being processedmaiY vary to a considerable extent, and it is therefore desirable to provide means forjanalogous `variation in the configuration oftemperature-determining device 38. Insofarasthe sealngapparatus is concerned, `,the only physical variation of importance is :the extension ofzneck .Dortn 421m relation to cone portion AI. Variation inthe length .of this extension is possible through adjustment oi the position of neck portion 42 with relation to cone portion 4 I, which` may be effected through use of thumb screw 46. Thus theposition of thermocouple 43 in relation to the localized heat source at the operating station currently occupied by Work-holder I3 :maybe regulated exactly to `insure correct registration of the heat-.treating temperature. i

As shown in Figure l, temperature-determining device 38, when installed` in workholder I3, rotates with the work-holder. `For convenience in reading temperature-indicating device 44,.,it1s desirable to provide for arrestment ofthe rotation of cone portion 4I and neck portion42` without impedng the rotation of work-holder I3. Rotary bearings 49 and 5,2 provide fricticnalncou- `pling between work-holder I3 and device 38 `and permit the operator to arrest device 38 independ-l ently of rotation of Ywork-holder I3 by simply grasping temperature-indicating device 44. This provision for arrestment of temperature-deter- `mining device 38 independently of rotation of work-holder I3 is useful when a chain drive'is employed since, in that event, it is not possible to arrest rotation ofwork-holder-I3 without iamming linkage I1 and therefore simultaneously arresting all other work-holders in the apparatus. When connecting means 28 and-linkage `lfI provide for frictional coupling as is the case-When a belt drive is employed, it is possible to arrest the rotary motion `of work-holder I3-without affecting the rotation of the other work-holders in the system. In such a case there is nonecessity for providing frictional coupling between work-holder I3 and temperature-determining device 38, and ange 4l, frame member' 48, and ` bearings 49 and 52 are not required.

In practice, the exact temperature gradations of the required heat-treating cycle are determined by calculation or from experience, and the localized heat sources, such as heat source I9. are adjusted to approximate the desired temperature at each Yof the operating stationsl, l l, etc. of .the sealing apparatus. Temperaturedetermining device 38 is then installed in one of the work-holders and proceeds through the heat-treating cycle, registering the temperature 4developed at each of the operating stations. Dev1- ations from'the required temperatures are noted and fine adjustments are made until a complete testV run with device 38 indicates accurate presetting of the heat-treating temperatures at all operating stations. Device 38 may then be removed from the work-holder, if the operator so desires, and the sealing apparatus may be utilized for sealing electron gun mount assemblies into cathode-ray tube envelopes Without encountering excessive breakage due to uncontrolled heat stresses.

Experience has indicated that once the proper heat-treating temperatures have been accurately established, the sealing operation may be continued for several hours Without signicant diniculty. However, since the localized heat sources 'are' adjustable and are somewhat subject to `uncalculated variation, it is possible that they ving heat-treating temperatures at the individual operating stations.

The arrangement and coniiguration of the improved apparatus for sealing electron guns into cathode-ray tube envelopes as described enables the operator to maintain an accurate check on the exact heat-treating temperature at each operating station at the precise position desired. It

is not necessary that the operator exercise particular skill or judgment in the positioning of a thermally sensitive device such as a contact pyrometer; he is therefore free to concentrate on properly observing and recording the temperature itself. The invention permits accurate determination of the critical temperatures of the sealing process in their predetermined sequence without requiring elaborate and complex individual installations at each operating station. It fur- `ther permits determination of those temperatures While requiring only intermittent attendance by a single operator. Use of the invention has effected a substantial reduction in the num- ;ber of ilaWs produced in operation of the process andhas led to a consequent marked reduction in the losses therefrom.

While a particular embodiment of the present invention has been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects, and, therefore, the aim in the appended claims isto coverall such changes and modications as fall Within the true spirit and scope Iclaim: Y 1. Apparatus for sealing electrode systems into electron-discharge device envelopes including: a

plurality of operating stations, each having at least one localized heat source, arranged in predetermined sequence for subjecting said envelopes to a predetermined heat-treating cycle; a

plurality of spaced rotatable Work-holders relatively movable With respect to said operating stations for transferring said envelopes and said electrode systems to each of said operating stations in sequence; driving apparatus for rotating said work-holders; a support member, generally simulating one of said envelopes in physical conguration, removably installed in one of said of the invention.

, work-holders; a temperature-indicating device mounted on said support member; a thermally sensitive device operatively connected to said temperature-indicating device and fixed to said support member in a position to register the heat treating temperature at the particular operating station momentarily occupied by said one rotatable work-holder; and friction coupling means between said driving apparatus and said support member to permit arrestment of rotation of said support member independently of rotation of the remainder of said work-holders.

2. Apparatus for sealing electrode systems into electron-discharge device envelopes including: a plurality of operating stations, each having at least one localized heat source, arranged in predetermined sequence for subjecting said envelopes to a predetermined heat-treating cycle; a plurality of spaced rotatable Work-holders relatively movable with respect to said operating stations for transferring said envelopes and said electrode systems to each of said operating stations in sequence; driving apparatus for rotating said Work-holders; a support member, generally simulating one of said envelopes in physical coniiguration, removably installed in one of said work-holders; a temperature-indicating device mounted on said support member; a thermally sensitive device operatively connected to said temperature-indicating device and fixed to said support member in a position to register the heat treating temperature at the particular operating station momentarily occupied by said one rotatable work-holder; and friction coupling means between said work-holder and said support member to permit arrestment of rotation of said support member independently of rotation of said work-holder.

3. Apparatus for sealing electron gun mounts into cathode-ray tube envelopes including: a plurality of operating stations, each having at least one localized heat source, arranged in predetermined sequence for subjecting said envelopes to a predetermined heat-treating cycle; a plurality of spaced'rotatable work-holders relatively movable with respect to said operating stations for transferring said envelopes and said electron gun mounts to each of said operating stations in sequence; driving apparatus for rotating said Workholders; a support member, generally simulating a cathode-ray tube envelope in physical conguration, removably installed in one of said workholders; a temperature indicating device mounted on said support member; a thermally sensitive device operatively connected to said temperature-indicating device and iixed to said support member in a position to register the heat treating temperature at the particular operating station momentarily occupied by said one rotatable work-holder; and means, including at least one friction coupling device, for coupling said driving apparatus to said one work-holder and for coupling said one work-holder to said support member to permit arrestment of rotation of said support member independently of rotation of the remainder of said work-holders.

4. Apparatus for sealing electrode systems into electron-discharge device envelopes including: a plurality of operating stations, each having at least one localized heat source, arranged in predetermined sequence for subjecting said envelopes to a predetermined heat-treating cycle; a plurality of spaced rotatable work-holders relatively movable with respect to said operating stations for transferring said envelopes and said electrode systems to each of said operating stations in sequence; driving apparatus for rotating said work-holders; a support memberl generally simulating one of said envelopes in physical configuration, removably installed in one of said work-holders; a temperature-indicating device mounted on said support member; a thermally sensitive device operatively connected to said temperature-indicating device and fixed to said support member in a position to register the heat treating temperature at the particular operating station momentarily occupied by said one rotatable Work-holder; a peripheral frame member adapted to be supported in said Work-holder and frictionally coupled to said support member and providing support therefor; and a rotary bearing having an inner race in engagement with said support member and an outer race engaged by said Work-holder, whereby rotation of said support member may be arrested independently of rotation of said work-holder.

5. Apparatus for sealing electrode systems into electron-discharge device envelopes including: a plurality of operating stations, each having at least one localized heat source, arranged in predetermined sequence for subjecting said envelopes to a predetermined heat-treating cycle; a plurality of spaced rotatable work-holders relatively movable with respect to said operating stations for transferring said envelopes and said electrode systems to each of said operating stations in sequence; driving apparatus for rotating said work-holders; a support member, generally simulating one of said envelopes in physical configuration, removably installed in one of said work-holders; a temperature-indicating device mounted on said support member; a thermally sensitive device operatively connected to said temperature-indicating device and fixed to said support member in a position to register the heat treating temperature at the particular operating station momentarily occupied by said one rotatable work-holder; an outwardly extending nange fixed to said support member; a frame member retained by said flange; a rst rotary bearing supported by said frame member in engagement with said support member when said support member is installed in said work-holder; and another rotary bearing having an inner race in engagement with said Work-holder, whereby rotation of said support member may be arrested independently of rotation of said workholder.

6. In apparatus for sealing electrode systems into electron-discharge device envelopes, of the type comprising a plurality of rotatable workholders in juxtaposition with respective localized heat sources: a support member generally simulating one of said envelopes in physical configuration; a temperature-indicating device mounted on said support member; a thermocouple operatively connected to said temperature-indicating device and adiustably fixed to said support member in a position to register the heat-treating temperature of said localized heat source when said support member is installed in one of said work-holders; and friction coupling means between said work-holder and said support member to permit arrestment of rotation of said support member independently of rotation of the remainder of said work-holders.

7. In apparatus for sealing electrode systems into electron-discharge device envelopes, of the type comprising at least one rotatable workholder in juxtaposition with at least one localized heat source: a support member generally simulating one of said envelopes in physical configuration; a temperature-indicating device mounted on said support member; a thermally sensitive device operatively connected to said temperatureindicating device and fixed to said support member in a position to register the heat-treating temperature of said localized heat source when said support member is installed in said workholder; a peripheral frame member adapted to be supported in said Work-holder and frictionally coupled to said support member and providing support therefor; and a rotary bearing having an inner race in engagement with said support member and an outer race engaged by said workholder, whereby rotation of said support member may be arrested independently of rotation of said work-holder.

8. In apparatus for sealing electron gun mounts into cathode-ray tube envelopes, of the type comprising at least one rotatable work-holder in juxtaposition with at least one localized heat source: a support member comprising a cone portion and a neck portion and generally simulating a cathode-ray tube envelope, said neck portion being axially adjustable with respect to said cone portion; a temperature-indicating device mounted on said support member a thermocouple operatively connected to said temperature-indicating device and xed to said neck portion in a position to register the heat-treating temperature of said localized heat source when said support member is installed in said work-holder; an outwardly extending flange affixed to said cone portion; a frame member retained by said flange; a first rotary bearing supported by said frame member in engagement with said cone portion when said support member is installed in said work-holder; and another rotary bearing having an inner race in engagement with said neck portion and an outer race engaged by said workholder, whereby rotation of said support member may be arrested independently of rotation of said work-holder.

JOHN F. DE ANO.

References Cited in the file of this patent UNITED STATES PATENTS Malloy Jan. 20, 1948

Images